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1 /* ===----- trampoline_setup.c - Implement __trampoline_setup -------------===
2  *
3  *                     The LLVM Compiler Infrastructure
4  *
5  * This file is dual licensed under the MIT and the University of Illinois Open
6  * Source Licenses. See LICENSE.TXT for details.
7  *
8  * ===----------------------------------------------------------------------===
9  */
10 
11 #include "int_lib.h"
12 
13 extern void __clear_cache(void* start, void* end);
14 
15 /*
16  * The ppc compiler generates calls to __trampoline_setup() when creating
17  * trampoline functions on the stack for use with nested functions.
18  * This function creates a custom 40-byte trampoline function on the stack
19  * which loads r11 with a pointer to the outer function's locals
20  * and then jumps to the target nested function.
21  */
22 
23 #if __ppc__ && !defined(__powerpc64__)
24 COMPILER_RT_ABI void
__trampoline_setup(uint32_t * trampOnStack,int trampSizeAllocated,const void * realFunc,void * localsPtr)25 __trampoline_setup(uint32_t* trampOnStack, int trampSizeAllocated,
26                    const void* realFunc, void* localsPtr)
27 {
28     /* should never happen, but if compiler did not allocate */
29     /* enough space on stack for the trampoline, abort */
30     if ( trampSizeAllocated < 40 )
31         compilerrt_abort();
32 
33     /* create trampoline */
34     trampOnStack[0] = 0x7c0802a6;    /* mflr r0 */
35     trampOnStack[1] = 0x4800000d;    /* bl Lbase */
36     trampOnStack[2] = (uint32_t)realFunc;
37     trampOnStack[3] = (uint32_t)localsPtr;
38     trampOnStack[4] = 0x7d6802a6;    /* Lbase: mflr r11 */
39     trampOnStack[5] = 0x818b0000;    /* lwz    r12,0(r11) */
40     trampOnStack[6] = 0x7c0803a6;    /* mtlr r0 */
41     trampOnStack[7] = 0x7d8903a6;    /* mtctr r12 */
42     trampOnStack[8] = 0x816b0004;    /* lwz    r11,4(r11) */
43     trampOnStack[9] = 0x4e800420;    /* bctr */
44 
45     /* clear instruction cache */
46     __clear_cache(trampOnStack, &trampOnStack[10]);
47 }
48 #endif /* __ppc__ && !defined(__powerpc64__) */
49